T lymphocytes are an essential part of the immune response as they are necessary for initiating the cellular response to pathogenic organisms, host cells that have become oncogenic and damaged tissue (see Fundamental Immunology, 6th Edition, 2003, ed. Paul, Wm. Lippencott Williams & Wilkins). Functionally, T cells have been subdivided into two classes with distinct surface antigens, CD4 and CD8 and this differentiation occurs in the Thymus. CD4+ cells are helper T cells and are further divided into Th1, Th2 and Th17 (see Tesmer, L. A., et al. (2008) Immunological Reviews, 228,87-113, Harington, L. et al. (2005) Nat. Immunol. 6,1123) which produce distinct levels of different cytokines (see below). CD8+ cells are cytolytic cells and are involved in lysis of tumors or viral infected cells. These responses are usually initiated by the interaction of a specific surface protein of the T cell, the T cell Receptor, TCR, (Davis, M. and Bjorkman, P. (1988) Nature 334, 395) with a “foreign” antigen on a defective host cell or on an Antigen Presenting Cell, APC, in the context of surface proteins of the Major Histocompatablilty Complex I or II (MHC I or II) and other proteins in a complex structure, the Immune Synapse (Grakoui, A, et al., (1999) Science 285,221). When the TCR interacts with a cognate antigen, it triggers a series of responses leading to activation of the T cell (Weiss, A. et al. (1991) Semin. Immulol. 3, 313, Weiss, A, (2003) Ann. Rev. Immunology). Activated T cells are induced to replicate more rapidly and, especially in the case of CD4+ cells, produce signaling proteins that are stimulatory (cytokines) or chemoattractive (chemokines) to inflammatory cells (i.e. lymphocytes, PMNLs, macrophage and monocytes) (Cook, D. N. (1996) J. Leukocyte Biol. 59,61, Friedman, et al. (2006) Nat. Immunol. 7, 1101).
T cell activation can result in a disease process. In animal models T cell responses described above have been shown to result in the inflammation of various tissues leading to experimental diseases resembling, among others, asthma and COPD, rheumatoid arthritis, psoriasis, atopic dermatitis, uveitis, and multiple sclerosis. (Barnes, P. (2008) Nat. Rev. Immunol. 8,183; Martin (2003) Paediatric Respiratory Reviews, 5;S47). Furthermore, activated T cells and the relevant cytokines have been identified in the corresponding human diseases (Barnes, P (2008) Nat. Rev. Immunol. 8;183; Krueger, J G and Bowcock (2005) Ann. Rev. Rheum. Dis. 64;30,13,14). T cells are directly activated by foreign MHC I and II as well as other antigens on transplanted tissues (liver, kidney, heart, etc.) resulting in graft rejection response which can be blocked by T cell specific antibodies and/or by drugs known to block T cell activation (Odum, J. et al. (1993) Clin Nephrol. 39:230; Passerini, P. and Ponticelli, C. (2001) Curr Opin Nephrol Hypertens.10(2):189-93). T cell recruitment of macrophages is involved in pancreatic lesions leading to loss of β-cells and Type 1 diabetes (Cantor, J. and Haskins, K. (2006) Drug Discovery Today: Disease Mechanisms 3;381). In addition, T cells can become oncogenic, resulting in T cell Lymphomas and Leukemias which in many instances are fatal (see Cheson, B. (2007) Sem. In Oncol. 34sup5; S3-S7).
Following the interaction of the T cell receptor, a series of kinases and other enzymes is activated resulting in the transport to the nucleus and/or activation of the transcription factors NFkappaB, NFAT and AP1 which causes transcription of cytokine and chemokine genes, as well as genes involved in T cell replication, motility and survival (Cordronniere, N. et al. (2000) Proc. Nat. Acad. Sci. 97;3394, Wulfing, C. and Davis, M. M. (1998) Science 282;2266). The serine/threonine kinase PKC theta, is an essential step in this pathway (Sun et al. (2000) Nature 404:402-7,19) and PKC theta deficient mice do not mount a T cell-driven inflammatory response (Healy, A. M. et al. (2006) J. Immunol. 177;1886, Anderson, K. et al. (2006) Autoimmunity 39;429). Human T cell lymphomas appear to have an upregulated PKCθ pathway (Vacca, A., et al. (2006) The EMBO Jour. 25, 1000) and mice deleted for PKCθ have reduced incidence of T cell lymphoma (Felli, P. M., et al. (2005) Oncogene 24;992). Blocking the function of PKCθ may be a therapy for several diseases in which T cells are involved.
It has also been shown that PKCθ activation in skeletal muscle may be involved in Type II diabetes (Li Y., et al. (2004) J. Biol. Chem. 279;45304), hence other diseases might be ameliorated by a inhibiting PKCθ.
The PKC family of serine/threonine kinases is comprised of at least 11 members grouped into three subfamilies based on their cofactor requirements: Conventional (alpha, beta1 and 2, gamma), novel (delta, epsilon, eta, theta) and atypical (xi, iota and zeta) (Newton, A. (2003) Biochem. J. 370;361.), which are structurally similar, but are necessary for many distinct cellular processes that are essential for cellular differentiation, survival and other specific cellular functions. For example, the novel PKC delta whose structure is most similar to PKC theta, appears to be essential for regulating replication of B lymphocytes (B cells) and reduced PKC delta causes uncontrolled expansion of B cells leading to B cell invasion of tissues similar to Systemic Lupus Erythematosis (Mecklenbräuker, I. et al. (2002) Nature 416;860; Miyamoto, A., et al., (2002) Nature 416;859). Conversely, the conventional PKC beta is necessary for B cell replication and survival (Saijo, vK., et al. (2003) Ann. N.Y. Acad. Sci. 987;125). Hence, although it is apparent that blocking of PKC theta may be therapeutic for diseases involving T cell activation, there is a need for isozyme-specific PKC theta inhibitors, in particular inhibitors of PKC-theta that have minimal activity on PKC-delta and beta. Surprisingly, the present invention meets this, and other, needs.